Nprs transmission method and device therefor

ABSTRACT

In the transmission of a narrowband positioning reference signal (NPRS), by a base station, in a cellular mobile communication system supporting narrowband-Internet of Things (NB-IoT), the base station transmits an NPRS by using a predetermined part of a sequence defined by a generation formula, which is the same as a positioning reference signal (PRS) generation formula, and when a PRS and the NPRS are transmitted through the same cell, the base station transmits, to a terminal, information indicating whether the PRS and the NPRS can be used together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/320,452, filed on Jan. 24, 2019, which is the National Stage filingunder 35 U.S.C. 371 of International Application No. PCT/KR2017/008115,filed on Jul. 27, 2017, which claims the benefit of U.S. ProvisionalApplication No. 62/371,849, filed on Aug. 8, 2016, 62/400,626, filed onSep. 28, 2016, 62/452,390, filed on Jan. 31, 2017, 62/454,057, filed onFeb. 3, 2017, and 62/457,180, filed on Feb. 10, 2017, the contents ofwhich are all hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to narrow band communication forsupporting Internet of Things (IoT) in a next generation wirelesscommunication system, and more particularly, to a method fortransmitting a narrowband positioning reference signal (NPRS) used fornarrowband IoT communication and a device therefor.

BACKGROUND ART

Recently, demand for IoT technology has increased and narrowband IoT(NB-IoT) technology has been discussed in order to support such an IoTservice. NB-IoT seeks to provide appropriate throughput betweenconnected apparatuses despite low apparatus complexity and low powerconsumption.

In 3GPP of the NB-IoT standards, NB-IoT technology capable of beingcombined with other 3GPP technologies such as GSM, WCDMA or LTE has beenstudied. To this end, a resource structure which will be used from theviewpoint of a legacy system has been discussed.

FIG. 1 is a diagram illustrating three modes which may be used inNB-IoT.

In order to satisfy the above-described demand, in NB-IoT, a channelbandwidth of 180 kHz is being considered for use both on uplink anddownlink, which corresponds to one physical resource block (PRB) in anLTE system.

As shown in FIG. 1, NB-IoT may support three modes such as standaloneoperation, guard band operation and inband operation. In particular, inthe inband mode shown in the lower side of FIG. 1, NB-IoT operation maybe performed through a specific narrowband in an LTE channel bandwidth.

In addition, in NB-IoT, using an extended DRX cycle, half-duplex FDD (HDFDD) operation and a single receive antenna in a wireless apparatussubstantially reduces power and cost.

DISCLOSURE Technical Problem

It is preferable to provide transmission of a positioning referencesignal (PRS) to support an operation of the NB IoT described as above.To this end, it is required to discuss how to configure a PRS in thelegacy LTE operation and a PRS for the operation of the NB IoT, how todefine a detailed transmission method, and how to define a relation withanother RS for the operation of the NB IoT.

Technical Solution

To achieve the object of the present invention, a method fortransmitting a narrowband positioning reference signal (NPRS) from abase station in a cellular mobile communication system supportingnarrowband-Internet of Things (NB-IoT) according to one aspect of thepresent invention comprises transmitting a positioning reference signal(PRS) by using a sequence defined by a first equation; transmitting theNPRS by using a predetermined part of the sequence defined by the firstequation; and transmitting, to a UE, information indicating whether thePRS and the NPRS can be used together when the PRS and the NPRS aretransmitted through the same cell.

The NPRS may be transmitted using a predetermined part determined inaccordance with a physical resource block (PRB) of the sequence, whichincludes the NPRS, if the cell is operated in an in-band mode, and theNPRS may be transmitted using a predetermined part determined regardlessof a position of the PRB which includes the NPRS if the cell is operatedin a stand-alone mode.

The NPRS may be transmitted per symbol by extracting two components ofthe sequence.

The method may further comprise transmitting position information of thePRB, which includes the NPRS, to the UE.

The NPRS may be transmitted per symbol from a first symbol of a firstsubframe if the cell is operated in a stand-alone mode or a guard bandmode, and the NPRS may be transmitted from a symbol except first one ormore predetermined number of symbols of a second subframe if the cell isoperated in an in-band mode.

When a frequency domain position to which the NPRS is transmitted is k,k=6m+(6−l+v_(shift))mod 6 is satisfied, where m is 0 or 1, l denotes asymbol index to which the NPRS is transmitted, and v_(shift) may bedetermined based on ID of a cell to which the NPRS is transmitted.

The first equation may be a pseudo-random sequence generation equationin which an initial value is determined by an identifier of the cell.

In another aspect of the present invention, a method for receiving anarrowband positioning reference signal (NPRS) by a user equipment (UE)from a base station in a cellular mobile communication system supportingnarrowband-Internet of Things (NB-IoT) comprises receiving, from thebase station, a positioning reference signal (PRS) corresponding to asequence defined by a first equation; receiving, from the base station,the NPRS corresponding to a predetermined part of the sequence definedby the first equation; and performing position estimation by using thePRS and the NPRS if information indicating that the PRS and the NPRS canbe used together is received from the base station.

The NPRS may be received using a predetermined part determined inaccordance with a physical resource block (PRB) of the sequence, whichincludes the NPRS, if the cell is operated in an in-band mode, and theNPRS may be transmitted using a predetermined part determined regardlessof a position of the PRB which includes the NPRS if the cell is operatedin a stand-alone mode.

The NPRS may correspond to two components of the sequence, and may betransmitted per symbol.

The method may further comprise receiving position information of thePRB, which includes the NPRS, from the base station.

The NPRS may be transmitted per symbol from a first symbol of a firstsubframe if the cell is operated in a stand-alone mode or a guard bandmode, and the NPRS may be transmitted per symbol from a symbol exceptfirst one or more predetermined number of symbols of a second subframeif the cell is operated in an in-band mode.

When a frequency domain position to which the NPRS is transmitted is k,k=6m+(6−l+v_(shift))mod 6 is satisfied, where m is 0 or 1, l denotes asymbol index to which the NPRS is transmitted, and may be determinedbased on ID of a cell to which the NPRS is transmitted.

In still another aspect of the present invention, a base station fortransmitting a narrowband positioning reference signal (NPRS) in acellular mobile communication system supporting narrowband-Internet ofThings (NB-IoT) comprises a processor configured to configure apositioning reference signal (PRS) by using a sequence defined by afirst equation and configure the NPRS by using a predetermined part ofthe sequence defined by the first equation; and a transceiver configuredto transmit the PRS and the NPRS to one or more user equipments (UEs),wherein the processor is configured to transmit, to the UE, informationindicating whether the PRS and the NPRS can be used together, throughthe transceiver when the PRS and the NPRS are transmitted through thesame cell.

In further still another aspect of the present invention, a userequipment (UE) for receiving a narrowband positioning reference signal(NPRS) from a base station in a cellular mobile communication systemsupporting narrowband-Internet of Things (NB-IoT) comprises atransceiver configured to receive, from the base station, a positioningreference signal (PRS) corresponding to a sequence defined by a firstequation and receive, from the base station, the NPRS corresponding to apredetermined part of the sequence defined by the first equation; and aprocessor configured to perform position estimation by using the PRS andthe NPRS if information indicating that the PRS and the NPRS can be usedtogether is received from the base station through the transceiver.

Advantageous Effects

According to the present invention described as above, an NPRS for anoperation of NB IoT may be transmitted or received more efficiently in anext generation wireless communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating three modes which may be used inNB-IoT;

FIGS. 2 and 3 are diagrams illustrating PRS transmission patterns;

FIG. 4 is a diagram illustrating a method for transmitting NPRS inaccordance with one embodiment of the present invention;

FIG. 5 is a diagram illustrating a configuration of NPRS per NB-IoToperation mode in accordance with one embodiment of the presentinvention;

FIG. 6 is a diagram illustrating a method for receiving NB-IoT downlinkreference signals in a UE in accordance with one embodiment of thepresent invention; and

FIG. 7 is a block diagram illustrating elements of a transmitting device10 and a receiving device 20, which implement the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description set forth below in connection withthe appended drawings is intended as a description of exemplaryembodiments and is not intended to represent the only embodimentsthrough which the concepts explained in these embodiments can bepracticed.

The detailed description includes details for the purpose of providingan understanding of the present invention. However, it will be apparentto those skilled in the art that these teachings may be implemented andpracticed without these specific details. In some instances, well-knownstructures and devices are omitted in order to avoid obscuring theconcepts of the present invention and the important functions of thestructures and devices are shown in block diagram form.

As described above, the present invention relates to a method fortransmitting a PRS used for narrowband IoT communication, that is, aNarrowband Positioning Reference Signal (NPRS) and a device therefor.

The 3GPP LTE standard supports a coverage enhancement (CE) scheme forsupporting UEs, which experience very great path-loss/penetration-loss,considering installation environments of various IoT/MTC UEs. As a mainscheme, a channel such as PDCCH/PDSCH transmitted to each UE and achannel such as PUSCH/PUCCH transmitted by each UE are repeatedlytransmitted over a plurality of subframes or resource units (RUs) tosupport coverage of maximum 15 dB or more.

Particularly, the LTE NB-IoT system uses a bandwidth of 180 kHz (1RB:180 kHz=15 kHz×12 RE), and may operate in a mode such as Stand-aloneoperation, Guard band operation, and In-band operation (same cell-ID,different cell-ID). Also, the NB-IoT system enables Multiple PRBtransmission and a base station may simultaneously use Multiple PRBs,whereas RF of NB-IoT UE enables narrowband reception (bandwidth of about200 kHz), and hopping of multiple PRBs may be performed by RF tuning.There are a PRB dedicated for data transmission as well as a PRB towhich a synchronization signal, system Information, etc. aretransmitted. OFDM symbols having a normal CP are used, and a subframeincludes 14 OFDM symbols.

Hereinafter, a PRS which is newly defined for NB-IoT operation isdefined as NPRS. The NPRS may be defined in NB-IoT PDSCH. In the in-bandoperation, NB-IoT is not used for first three OFDM symbols of a subframeon the assumption that PDCCH of the LTE system is transmitted, and it ispreferable that data are not transmitted to an LTE CRS position. In thein-band operation mode, the NB-IoT UE may use LTE CRS.

In the NPRS transmission scheme which will be described hereinafter, areusable structure considering a PRS transmission scheme of the LTEsystem and a relation between the NPRS transmission scheme and the PRStransmission scheme will be defined.

LTE-PRS

A Positioning Reference Signal (PRS) defined in the 3GPP LTE Release-9has been designed similarly to a cell-specific reference signal definedin the LTE Release-8. Pseudo-random QPSK sequences arranged at a spacingof 6 REs and frequency-shifted in accordance with Cell-ID, having a seeddetermined in accordance with Cell-ID are mapped into one OFDM symbol.The pseudo-random QPSK sequences are transmitted to OFDM symbols exceptOFDM symbol to which PDCCH and cell-specific reference signal aretransmitted, and are shifted in a frequency domain every OFDM symbol.The PRS is transmitted at N continuous subframes (N=1,2,4,6), and atransmission period of 160, 320, 640, and 1280 subframes is defined. Afirst one of PRS transmission subframes is determined by a function of atransmission period, a PRS subframe offset and a system frame number. APRS bandwidth may be 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHZ, 20 MHz, orthe like. When it is assumed that a transmission period is 160 ms, 6continuous subframes may be used at a PRS bandwidth of 1.4 MHz. A longtransmission period increases a UE response time. The LTE defines interfrequency measurement.

FIGS. 2 and 3 are diagrams illustrating PRS transmission patterns.

Specifically, FIG. 2 illustrates a PRS transmission pattern when anormal CP is used, and FIG. 3 illustrates a PRS transmission patternwhen an extended CP is used.

The PRS is defined through a pseudo-random sequence generation Equationas follows.

$\begin{matrix}{{r_{l,n_{3}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2\; m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {{1 - {2 \cdot {c\left( {{2\; m} + 1} \right)}}},\mspace{20mu} {m = 0},1,\ldots \mspace{11mu},{{2\; N_{RB}^{{{ma}\; x},{DL}}} - 1}} \right.}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In this case, n_(s) denotes a slot number within a radio frame, 1 withinthe slot denotes an OFDM symbol number, and N_(RB) ^(max_DL) denotes amultiple of subcarriers per RB in case of the greatest downlinkbandwidth configuration.

In the Equation 1, c(i) follows a definition of pseudo-random sequencedefined in the LTE, and an initial value may be defined in accordancewith cell ID.

The sequence defined as above may be mapped into a complex modulationsymbol a_(k,l) ^((p)) as follows.

a _(k,l) ^((p)) =r _(l,n) _(s) (m′)  [Equation 2]

In this case, if the normal CP is used, the following Equation isestablished.

$\begin{matrix}{{k = {{6\left( {m + N_{RB}^{DL} - N_{RB}^{PRS}} \right)} + {\left( {6 - l + v_{shift}} \right){mod}\; 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} \left( {1\mspace{14mu} {or}\mspace{14mu} 2\mspace{14mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)}} \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} \left( {4\mspace{14mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)}}\end{matrix}m} = 0},1,\ldots \mspace{11mu},{{{2 \cdot N_{RB}^{PRS}} - {1m^{\prime}}} = {m + N_{RB}^{{{ma}\; x},\; {DL}} - N_{RB}^{PRS}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Meanwhile, if the extended CP is used, the following Equation isestablished.

$\begin{matrix}{{k = {{6\left( {m + N_{RB}^{DL} - N_{RB}^{PRS}} \right)} + {\left( {5 - l + v_{shift}} \right){mod}\; 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{1,2,4,5} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} \left( {1\mspace{14mu} {or}\mspace{14mu} 2\mspace{14mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)}} \\{2,4,5} & {{{if}\mspace{14mu} n_{s}\; {mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} \left( {4\mspace{14mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)}}\end{matrix}m} = 0},1,\ldots \mspace{11mu},{{{2 \cdot N_{RB}^{PRS}} - {1m^{\prime}}} = {m + N_{RB}^{{{ma}\; x},\; {DL}} - N_{RB}^{PRS}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In this case, N_(RB) ^(PRS) which denotes a bandwidth of the PRS followsa higher layer signal, and satisfies v_(shift)=N_(ID) ^(cell) mod 6.

In this way, the PRS may be transmitted as shown in FIGS. 2 and 3.

In the NB-IoT system, PRS transmission subframes are defined, and amethod for using PRS transmission subframes of the LTE system in thein-band operation is suggested.

Method for Transmitting NPRS

FIG. 4 is a diagram illustrating a method for transmitting NPRS inaccordance with one embodiment of the present invention.

In a cellular mobile communication system that supports NB-IoT, a basestation may transmit a Positioning Reference Signal (PRS) as describedwith reference to FIGS. 2 and 3 in transmitting a Narrowband PositioningReference Signal (NPRS) or NB-IoT PRS (S410). This embodiment suggeststhat the NPRS for NB-IoT is transmitted using a sequence based on thesame Equation (e.g., the Equation 1) as that of the PRS, particularlysome components of the corresponding sequence to be matched with anNB-IoT operation band (S420).

In this way, the PRS and the NPRS, which are generated based on the sameEquation, may be used together. Therefore, this embodiment suggests thatthe base station transmits information indicating whether the PRS andthe NPRS can be used together to the UE if the PRS and the NPRS aretransmitted through the same cell.

In a system that allows physical channels respectively defined fordifferent RATs or various services to be multiplexed in the samecarrier, if the physical channels respectively defined for differentRATs or various services are multiplexed in the same carrier, and a partwithin a frequency resource used by a random RAT or a random physicalchannel is reserved by another RAT or another physical channel, a signaldefined by a specific RAT or a specific physical channel may be used bybeing shared by another RAT or another physical channel. Particularly,if NPDSCH is allowed to be transmitted from a part of a band to which3GPP LTE PDSCH is transmitted, a positioning reference signal (PRS)transmitted from the PDSCH may be transmitted from the NPDSCH, and theNB-IoT UE may use the PRS of the PDSCH.

A detailed method for configuring NPRS is as follows.

In one embodiment of the present invention, it is assumed that theNB-IoT PRS includes 14 OFDM symbols. Also, NB-IoT PRS subframe may betransmitted for a time period longer than a transmission period of LTEPRS subframe as much as N times. For example, if N=6, the NB-IoT systemmay transmit NB-IoT PRS at continuous subframes 6, 12, 24, and 36.

There may be a plurality of candidate PRBs to which NB-IoT PRS subframemay be transmitted. The PRS subframe may be transmitted to the candidatePRBs in a guard band as well as an in-band in the in-band operationmode. On the contrary, the PRS subframe transmission may also beindicated in a guard band and an in-band of the guard band operationmode. A candidate carrier to which the PRS subframe may be transmittedmay be designated even in case of the stand-along operation mode.

NB-IoT base station may set NB-IoT PRS subframe transmission period perindicated candidate PRB or candidate carrier. The NB-IoT UE may receiveNB-IoT PRS subframe in one PRB, and may receive NB-IoT PRS subframetransmitted from inter-PRB between NB-IoT PRS subframe transmissionperiods transmitted from the corresponding PRB.

If the NB-IoT UE intends to receive NB-IoT PRS subframes from aplurality of PRBs or a plurality of carriers, it may be assumed that aswitching time from a reference band or carrier to inter-band orinter-carrier and a switching time from inter-band or inter-carrier toreference band or carrier are required, and a PRS is received from theNB-IoT PRS subframe at a length of NB-IoT PRS subframe transmitted frominter-band or inter-carrier, which is shorter than a length of NB-IoTPRS subframe transmitted from reference band or reference carrier asmuch as N subframe (e.g., one subframe at the front and one subframe atthe rear—total two subframes). When the NB-IoT PRS subframe istransmitted to a plurality of bands or a plurality of carriers in theNB-IoT system, it is preferable that the number of NB-IoT PRS subframestransmitted from reference band or reference carrier is set to begreater than N subframes. That is, if NB-IoT PRS subframes aretransmitted from a plurality of PRBs or a plurality of carriers, and theNB-IoT UE receives NB-IoT UE PRS subframes by switching a plurality ofbands or a plurality of carriers, the PRS may be received for the lengthof the NB-IoT PRS subframe indicated by the reference band or thereference carrier. Afterwards, it is assumed that the NB-IoT UE receivesNB-IoT PRS for a time period shorter than a length of a subframedesignated at which NB-IoT PRS subframe of inter-band or inter-carrierwill be transmitted, on the assumption that each of the switching timeto inter-band or inter-carrier and the switching time to the referenceband or the reference carrier is included in the NB-IoT PRS subframereception time of the inter-band or the inter-carrier.

It is assumed that NB-IoT PRS is transmitted from 14 OFDM symbols in aPRB of stand-alone carrier and guard band and overlap of LTE PDCCH(assumption of 3 OFDM symbols) and LTE CRS (1Tx, 2Tx, 4Tx) is avoided inthe in-band.

The NB-IoT PRS is arranged at two of 12 REs, and two PRSs have a spacingof 6 REs on a frequency. (For example, 0-6, 1-7, 2-8, 3-9, 4-10, 5-11,etc.). The corresponding position is frequency-shifted in accordancewith Cell-ID. Also, the NB-IoT PRS has a pattern repeated in a unit of 7OFDM symbols. That is, a frequency position k is expressed ask=6×m+(6−n+vshift) mod 6, wherein m=0,1 if the number of PRSs per OFDMsymbol is 2, and n=0,1,2,3,4,5,6 if the number of OFDM symbols per slotis 7, and vshift=Ncell-ID mod 6 determined in accordance with cell-idmay be expressed. As a sequence used for the NB-IoT PRS, a pseudo-randomsequence defined in the LTE system is used, and a seed of sequencegeneration is determined by a function of a slot number (ns=0, 1, . . ., 19), OFDM symbol number (n=0, 1, 2, . . . , 6), cell ID and CP length.

One embodiment of the present invention suggests that a sequencecorresponding to a PRB position is used in case of an in-band operationmode and a sequence is used on the assumption that a PRB position isfixed in case of a stand-alone operation mode.

FIG. 5 is a diagram illustrating a configuration of NPRS per NB-IoToperation mode in accordance with one embodiment of the presentinvention.

As described above with reference to FIG. 1, NB-IoT operation includesan in-band mode operated by being included in an LTE band, a guard bandmode, and a stand-alone operation mode independently existing from theLTE band. In this embodiment described as above, it is assumed that ageneration equation of NPRS is configured using the same generationequation of PRS. In this state, this embodiment suggests that NPRS isconfigured using a partial component (two components per symbol) of asequence considering a position of PRB to which NPRS is transmitted incase of an in-band mode. In this way, in the in-band operation, NPRS isused for measurement together with PRS considering NPRS transmission PRBposition to improve throughput.

However, in case of the guard band mode or the stand-alone mode, sinceconsideration of a position to which NPRS is transmitted is not requiredas described above, two components per symbol may be extractedregardless of NPRS transmission position, whereby the NPRS may beconfigured.

Meanwhile, the NB-IoT PRS may be arranged at 4 of 12 REs, and 4 PRSs mayhave a spacing of three REs on a frequency. Frequency shift may beperformed in accordance with cell-ID.

In accordance with the above method, the NPRS may be transmitted byresource mapping as follows in one embodiment of the present invention.

First of all, if the NB IoT operation is performed in the in-band mode,the NPRS may be subjected to resource mapping as follows.

$\begin{matrix}{{k = {{6\; m} + {\left( {6 - l + v_{shift}} \right){mod}\; 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} \left( {1\mspace{14mu} {or}\mspace{14mu} 2\mspace{14mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)}} \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = {1\mspace{14mu} {and}\mspace{14mu} \left( {4\mspace{14mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)}}\end{matrix}m} = 0},{1{m^{\prime} = {m + {2\; n_{PRB}^{\prime}} + N_{RB}^{{{ma}\; x},{DL}} - \overset{\sim}{n}}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In this case, n′_(PRB) denotes a position of a PRB which includes NPRStransmitted through higher layer signaling. Also, if N_(RB) ^(DL) is anodd number, ñ=1 may be defined, and if N_(RB) ^(DL) is an even number,ñ=0 may be defined.

Also, if the NB IoT operation is performed in the guard band mode or thestand-alone mode, the NPRS may be subjected to resource mapping asfollows.

k=6m+(6−l+v _(shift))mod 6

l=0,1,2,3,4,5,6

m=0,1

m′=m+N _(RB) ^(max,DL)−1  [Equation 6]

That is, if the NB IoT operation is performed in the guard band mode orthe stand-alone mode, NPRS transmission symbols may be used from thefirst symbol, and the sequence may be defined regardless of a PRBposition for transmitting NPRS.

For the NB-IoT PRS, the base station may deliver PRS transmissionrelated information to the UE, wherein the corresponding information mayinclude a subframe length, a subframe period, a subframe offset, etc.Also, ID information used for RE mapping of the NB-IoT PRS and sequencedetermination may be different from ID applied to another channel of thecorresponding NB-IoT PRB, and may be notified independently.

Also, the base station may deliver PRS transmission informationtransmitted from a neighbor cell to the NB-IoT UE, wherein eachinformation may indicate a subframe length, a subframe period, asubframe offset, and an NB-IoT PRS transmission PRB position inconjunction with the corresponding Cell-ID.

In one embodiment of the present invention, the NB-IoT UE may expectthat a normal subframe of NB-IoT is not transmitted to a subframe towhich LTE PRS is transmitted.

Also, it may indicate that NB-IoT PRS is transmitted to a subframe towhich LTE PRS is transmitted, or may indicate that LTE PRS istransmitted from a subframe to which NB-IoT PRS is transmitted.

In one embodiment of the present invention, the base station mayindicate, to the NB-IoT UE, an operation mode of NB-IoT within a bandused by the LTE system. Alternatively, the base station may indicate aPRB, which can be used for channel and signal for NB-IoT, among PRBswithin a band of the LTE system. At this time, the base station mayindicate a PRB to which NB-IoT PRS can be transmitted, and the NB-IoT UEmay perform measurement by using a PRS transmitted from thecorresponding PRB.

The NB-IoT UE may expect that NB-IoT PRS subframe is not transmittedfrom LTE PRS subframe in the in-band operation (case that Cell-ID isdifferent from that of LTE). Particularly, this scheme may be appliedsuch that NPRS (NB-IoT PRS) may not be transmitted from a serving cellat a corresponding subframe if the serving cell notifies the NB-IoT UEof LTE PRS subframe information on a neighbor cell not the serving cell.

In the above embodiment, the number of NB-IoT PRS transmission subframesmay be more than the number of LTE PRS transmission subframes, and someor all subframes of the LTE PRS transmission subframes may be overlappedwith the time when NB-IoT PRS transmission subframes are transmitted.The base station may notify the NB-IoT UE of the presence of the LTE PRStransmission subframes.

Also, in the above embodiment, the base station may provide the UE withinformation on LTE PRS subframes. (e.g., cell-ID, subframe length,period, offset, bandwidth). Also, the base station may provide LTE PRSsubframe information of the neighbor cell. The UE may use LTE PRS forpositioning measurement, and the base station may notify the UE whetherthe LTE PRS may be used for measurement together with the NB-IoT PRS.Alternatively, if the base station notifies the UE of information on theLTE PRS, the UE may recognize that the LTE PRS may be used formeasurement together with the NB-IoT PRS. This operation may be appliedto the case that LTE PRS and NB-IoT PRS are comprised of the same PRS IDand/or the same cell ID and/or the same v shift. At this time, REmapping of the NB-IoT PRB and a sequence generation rule according toPRB position on a frequency axis may follow the LTE PRS.

Neighbor cell NBPRS PRB may be assumed to be the same as that of theserving cell, PRS may be shifted in accordance with cell ID, or PRSoffset information compared with the serving cell may be used.

In one embodiment of the present invention, the NB-IoT UE may use a CRSfor measurement. As conditions which can be used, the NB-IoT UE may usea CRS of the legacy LTE included in the subframe in case of the in-bandoperation mode.

In the above embodiment, Node-B in a status of intra-band (that is, thesame center between cells) provides neighbor cell Cell-ID to be measuredand PRS information (subframe length, period, offset, PRB information)of the neighbor cell regarding PRS. At this time, whether LTE CRSincluded in the in-band can be used may be notified. Alternatively, theUE operating in the in-band operation mode may use the CRS formeasurement on the assumption that the CRS is equally transmitted evenfrom the neighbor cell.

In the above embodiment, when the NB-IoT UE uses the legacy CRS formeasurement, one of two CRS ports that may be included in one OFDMsymbol may be used for measurement.

In another embodiment of the present invention, a signal defined in theNB-IoT may be used as the PRS.

For example, if a Narrowband Secondary Synchronization Signal (NSSS) maybe used as the PRS, candidate anchor PRB information (or information onPRB to which NSSS is transmitted) of the serving cell and correspondingNSSS sequence (or NB cell ID) and same information on the neighbor cellmay be transmitted to the UE. At this time, the base station mayindicate whether the NSSS included in in-band can be used.

Various Reference Signals for NB-IoT Operation and Relation Between theReference Signals

Meanwhile, hereinafter, various reference signals, which can be used forNB-IoT operation, as well as the aforementioned NPRS will be describedand a relation between the signals will be discussed.

First of all, in the NB IoT system, a Narrowband Reference Signal (NRS)has been newly defined for data demodulation and channel measurement,and the base station may indicate absolute value information of a powerof the NRS. Also, the embodiment of the present invention suggests thatthe NRS is always transmitted regardless of each mode, particularly LTECRS is additionally used for data demodulation together with the NRS inin-band operation. At this time, a problem may occur in that a sizevalue of an estimated channel is varied due to a power differencebetween the NRS and the LTE CRS. To solve this problem, power ratioinformation of the NRS and the LTE CRS may be indicated.

FIG. 6 is a diagram illustrating a method for receiving NB-IoT downlinkreference signals in a UE in accordance with one embodiment of thepresent invention.

First of all, the UE may receive the NRS through first type subframe(s)through a downlink (S610). The first type subframe(s) for receiving theNRS may be predefined subframes, or configuration information of thefirst type subframe may be received through system information.

Meanwhile, the UE may receive configuration information on second typesubframe(s), which can receive the NPRS, through a higher layer (S620).Therefore, the UE receives the NPRS at the second type subframe. Eventhough the second type subframe according to second type subframeconfiguration information is partially overlapped with the first typesubframe, the UE may be operated on the assumption that the NPRS is onlyreceived at the corresponding subframe and the NRS is not received. Thatis, the UE may be operated on the assumption that the NPRS is onlyreceived at the second type subframe (S630).

The NRS may be used for demodulation of NPDCCH/NPDSCH. Therefore, thefirst type subframe may be referred to as a normal subframe in NB-IoToperation or DL valid subframe. In the configuration of the generalsubframe and the configuration of the second type subframe for NPRStransmission, it is preferable to give a priority to the second typesubframe. Therefore, in one embodiment of the present invention, it isdefined that the NRS is not transmitted at a subframe according toconfiguration information of the second type subframe.

That is, the NB-IoT UE may expect that a normal subframe of NB-IoT isnot transmitted to a subframe to which NB-IoT PRS is transmitted, and adetailed operation example is as follows.

It is preferable that NRS (or NPDCCH/NPDSCH) is not transmitted to asubframe configured to allow NPRS (NB-IoT PRS) to be transmitted theretoeven though the subframe is configured as a DL valid subframe (subframeto which NRS is transmitted and to which NPDCCH/NPDSCH can betransmitted) of NB-IoT.

Alternatively, it is preferable that the NPRS is not transmitted to asubframe configured as a DL valid subframe even though the subframe isconfigured as a subframe to which the NPRS is transmitted.

Particularly, if NPDCCH/NPDSCH is scheduled to be repeatedly transmittedN times through a plurality of DL valid subframes which include thesubframe to which the NPRS is transmitted, the UE may operate byunderstanding that the NPDCCH/NPDSCH is transmitted through N DL validsubframes except the corresponding subframe.

The DL valid subframe of NB-IoT is a subframe used for DL transmissionof NB-IoT, and may be used as a normal subframe of NB-IoT, to whichNPDCCH/NPDSCH/NRS is transmitted, or a subframe to which NPRS istransmitted.

Also, the NB-IoT UE may expect that LTE CRS is not transmitted to thesubframe to which the NB-IoT PRS is transmitted.

Power Ratio of NRS and NPRS

If the NPRS and additional signals are used for measurement in NB IoT, aproblem may occur in that exactness of a measured value is reduced dueto a power difference between the NPRS and the corresponding signals. Tosolve this problem, information on a power between the NPRS and thecorresponding signal is required to use corresponding information.

For example, PRS_RA may be defined (PRS-to-RS EPRE ratio for the PRS inall transmitted OFDM symbols not containing CRS).

Also, a power ratio for the NRS and the NPRS is defined, wherein thepower ratio may be configured by offset of several steps.

NRS, LTE CRS, etc. may be transmitted to the subframe to which the NPRSis transmitted, and it is preferable that data are not transmitted tothe corresponding subframe.

A power (or energy) ratio of RE included in OFDM symbol to which NRS isnot transmitted, as compared with NRS power (or energy), may be definedand indicated. At this time, since the NPRS is transmitted to the OFDMsymbol to which the NRS is not transmitted, a transmission power ratioof the NPRS may be identified indirectly.

It is assumed that a power of RE included in OFDM symbol to which LTECRS is transmitted from PRB allocated for NB IoT transmission is equalto a power of RE included in OFDM symbol to which LTE CRS and NRS arenot transmitted.

If the LTE CRS is transmitted to the OFDM symbol to which the NPRS istransmitted, it is assumed that a transmission power of the NPRSincluded in the corresponding OFDM symbol is equal to the power of REincluded in the OFDM symbol to which LTE CRS and NRS are nottransmitted. In this case, it is assumed that the same NPRS transmissionpower is applied to the symbol to which the CRS is transmitted or thesymbol to which the CRS is not transmitted.

It is preferable that the NRS is not transmitted from the band orsubframe to which the NPRS is transmitted.

A transmission power for RE of OFDM symbol to which the NPRS istransmitted may be defined by a ratio for a power (or energy) of the NRSof the OFDM symbol included in the band or subframe to which the NRS istransmitted.

Also, in one embodiment of the present invention, a transmission powerratio of NPRS to other signals may be defined.

The transmission power ratio of the NPRS to other signals, such as NRS,LTE CRS, NPSS, NSSS, and LTE PRS, which may be used for measurement forpositioning together with the NPRS, may be defined. For example, if theNPRS is used together with the existing LTE PRS, a transmission powerratio of two channels may previously be defined (e.g., the UE assumesthat transmission powers of two channels are equal to each other), orthe base station may indicate a transmission power ratio of two channelsor a transmission power of each channel. For another example, when theNB IoT UE may receive information on LTE CRS transmitted within the bandused for the legacy LTE transmission from the network, the NB IoT UE mayindicate the transmission power ratio of the NPRS and the LTE CRS or atransmission power of each channel.

The power of the NRS may be limited to the power of the NRS transmittedto an anchor PRB to which the NB-IoT UE can initially access.

As described above, the power ratio may be defined and then delivered tothe UE through SIB or RRC signaling.

Apparatus Configuration

FIG. 7 is a block diagram showing the components of a transmittingdevice 10 and a receiving device 20 for performing embodiments of thepresent invention.

The transmitting device 10 and the receiving device 20 include radiofrequency (RF) units 13 and 23 for transmitting or receiving a radiosignal carrying information and/or data, a signal and a message,memories 12 and 22 for storing a variety of information associated withcommunication in a wireless communication system, and processors 11 and21 operatively connected to the components including the RF units 13 and23 and the memories 12 and 22 and configured to control the memories 12and 22 and/or the RF units 13 and 23 to perform at least one of theembodiments of the present invention, respectively.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/output signal.The memories 12 and 22 may be used as a buffer.

The processors 11 and 21 generally control the overall operation of thevarious modules of the transmitting device and the receiving device. Inparticular, the processors 11 and 21 may perform a variety of controlfunctions for performing the present invention. The processors 11 and 21may be referred to as a controller, a microcontroller, a microprocessor,a microcomputer, etc. The processors 11 and 21 can be implemented by avariety of means, for example, hardware, firmware, software, or acombination thereof. In the case of implementing embodiments of thepresent invention by hardware, application specific integrated circuits(ASICs), Digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), etc. configured to perform embodiments of thepresent invention may be included in the processors 11 and 21. Ifoperations or functions of embodiments of the present invention areimplemented by firmware or software, firmware or software may beconfigured to include modules, procedures, functions, etc. forperforming the functions or operations of embodiments of the presentinvention. The firmware or software configured to perform embodiments ofthe present invention may be included in the processors 11 and 21 orstored in the memories 12 and 22 so as to be operated by the processors11 and 21.

The processor 11 of the transmitting device 10 performs coding andmodulation with respect to a signal and/or data which is scheduled bythe processor 11 or a scheduler connected to the processor 11 to betransmitted to an external device and transmits the signal and/or datato the RF unit 13. For example, the processor 11 transforms a datastream to be transmitted into K layers via demultiplexing and channelcoding, scrambling, modulation, etc. The coded data stream is alsocalled a codeword and is equivalent to a transport block which is a datablock provided by a medium access control (MAC) layer. One transportblock (TB) is encoded into one codeword and each codeword is transmittedto the receiver in the form of one or more layers. For frequencyup-conversion, the RF unit 13 may include an oscillator. The RF unit 13may include N_(t) (N_(t) being a positive integer) transmit antennas.

Signal processing of the receiving device 20 is the inverse of signalprocessing of the transmitting device 10. Under control the processor21, the RF unit 23 of the receiving device 20 receives a radio signaltransmitted by the transmitting device 10. The RF unit 23 may includeN_(r) (N_(r) being a positive integer) receive antennas and the RF unit23 performs frequency down-conversion with respect to each signalreceived via each receive antenna and restores a baseband signal. The RFunit 23 may include an oscillator for frequency down-conversion. Theprocessor 21 may perform decoding and demodulation with respect to theradio signal received via the receive antennas and restore original datatransmitted by the transmitting device 10.

Each of the RF units 13 and 23 includes one or more antennas. Theantennas serve to transmit the signals processed by the RF units 13 and23 to external devices or to receive radio signals from external devicesand to send the radio signals to the RF units 13 and 23 under control ofthe processors 11 and 21 according to one embodiment of the presentinvention. The antennas are also called antenna ports. Each antenna maybe composed of one physical antenna or a combination of more than onephysical antenna elements. The signal transmitted by each antenna is notdecomposed by the receiving device 20. A reference signal (RS)transmitted in correspondence with the antenna defines the antennaviewed from the viewpoint of the receiving device 20 and enables thereceiving device 20 to perform channel estimation of the antennaregardless of whether the channel is a single radio channel from asingle physical antenna or a composite channel from a plurality ofphysical antennal elements including the above antennas. That is, theantenna is defined such that the channel for delivering a symbol overthe antenna is derived from the channel for delivering another symbolover the same antenna. In case of the RF unit supporting a multipleinput multiple output (MIMO) function for transmitting and receivingdata using a plurality of antennas, two or more antennas may beconnected.

In the embodiments of the present invention, a UE operates as thetransmitting device 10 in uplink and operates as the receiving device 20in downlink. In the embodiments of the present invention, an eNBoperates as the receiving device 20 in uplink and operates as thetransmitting device 10 in downlink. Hereinafter, the processor, the RFunit and the memory included in the UE are respectively referred to as aUE processor, a UE RF unit and a UE memory and the processor, the RFunit and the memory included in the eNB are respectively referred to asan eNB processor, an eNB RF unit and an eNB memory.

The detailed description of the exemplary embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the exemplary embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. Accordingly, the inventionshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

INDUSTRIAL APPLICABILITY

The invention described as above may be applied to various wirelesscommunication systems, which support a narrowband communication toprovide IoT services, as well as a wireless communication system whichprovides IoT services based on an LTE system.

What is claimed is:
 1. A method for transmitting a narrowbandpositioning reference signal (NPRS) from a base station in a cellularmobile communication system supporting narrowband-Internet of Things(NB-IoT), the method comprising: transmitting a positioning referencesignal (PRS) by using a first sequence defined by a first equation;transmitting the NPRS by using a part of a second sequence defined bythe first equation; and transmitting, to a UE, information on whetherthe PRS and the NPRS can be used together when the PRS and the NPRS aretransmitted through the same cell, wherein the part of the secondsequence is differently determined based on whether the cell is operatedin an in-band mode or in a stand-alone mode.
 2. The method of claim 1,wherein the NPRS is transmitted using a first part of the secondsequence determined by using a position of a physical resource block(PRB) for the NPRS, if the cell is operated in the in-band mode, andwherein the NPRS is transmitted using a second part of the secondsequence determined not using the position of the PRB, if the cell isoperated in the stand-alone mode.
 3. The method of claim 2, wherein theNPRS is transmitted per symbol by extracting two components of thesequence.
 4. The method of claim 2, further comprising transmittingposition information of the PRB to the UE.
 5. The method of claim 1,wherein the NPRS is transmitted per symbol from a first symbol of afirst subframe if the cell is operated in the stand-alone mode or aguard band mode, and the NPRS is transmitted from a symbol except firstone or more predetermined number of symbols of a second subframe if thecell is operated in the in-band mode.
 6. The method of claim 1, wherein,when a frequency domain position to which the NPRS is transmitted is k,k=6m+(6−l+v_(shift))mod 6 is satisfied, where m is 0 or 1, 1 denotes asymbol index to which the NPRS is transmitted, and v_(shift) isdetermined based on ID of a cell to which the NPRS is transmitted. 7.The method of claim 1, wherein the first equation is a pseudo-randomsequence generation equation in which an initial value is determined byan identifier of the cell.
 8. A method for receiving a narrowbandpositioning reference signal (NPRS) by a user equipment (UE) from a basestation in a cellular mobile communication system supportingnarrowband-Internet of Things (NB-IoT), the method comprising:receiving, from the base station, a positioning reference signal (PRS)corresponding to a first sequence defined by a first equation;receiving, from the base station, the NPRS corresponding to a part of asecond sequence defined by the first equation; and performing positionestimation by using the PRS and the NPRS based on information on thatthe PRS and the NPRS can be used together being received from the basestation, wherein the part of the second sequence is differentlydetermined based on whether the cell is operated in an in-band mode orin a stand-alone mode.
 9. The method of claim 8, wherein the NPRS isreceived using a first part of the second sequence determined by using aposition of a physical resource block (PRB) for the NPRS, if the cell isoperated in the in-band mode, and wherein the NPRS is received using asecond part of the second sequence determined not using the position ofthe PRB, if the cell is operated in the stand-alone mode.
 10. The methodof claim 9, wherein the NPRS corresponds to two components of thesequence, and is transmitted per symbol.
 11. The method of claim 9,further comprising receiving position information of the PRB from thebase station.
 12. The method of claim 8, wherein the NPRS is receivedper symbol from a first symbol of a first subframe if the cell isoperated in the stand-alone mode or a guard band mode, and the NPRS isreceived per symbol from a symbol except first one or more predeterminednumber of symbols of a second subframe if the cell is operated in thein-band mode.
 13. The method of claim 8, wherein, when a frequencydomain position to which the NPRS is received is k,k=6m+(6−l+v_(shift))mod 6 is satisfied, where m is 0 or 1, l denotes asymbol index to which the NPRS is received, and v_(shift) is determinedbased on ID of a cell to which the NPRS is received.
 14. A base stationfor transmitting a narrowband positioning reference signal (NPRS) in acellular mobile communication system supporting narrowband-Internet ofThings (NB-IoT), the base station comprising: a processor configured toconfigure a positioning reference signal (PRS) by using a first sequencedefined by a first equation and configure the NPRS by using a part of asecond sequence defined by the first equation; and a transceiverconfigured to transmit the PRS and the NPRS to one or more userequipments, UEs, wherein the processor is configured to transmit, to theUE, information on whether the PRS and the NPRS can be used together,through the transceiver, when the PRS and the NPRS are transmittedthrough the same cell, wherein the processor differently determines thepart of the second sequence based on whether the cell is operated in anin-band mode or in a stand-alone mode.
 15. A user equipment (UE) forreceiving a narrowband positioning reference signal (NPRS) from a basestation in a cellular mobile communication system supportingnarrowband-Internet of Things (NB-IoT), the UE comprising: a transceiverconfigured to receive, from the base station, a positioning referencesignal (PRS) corresponding to a first sequence defined by a firstequation and receive, from the base station, the NPRS corresponding to apart of a second sequence defined by the first equation; and a processorconfigured to perform position estimation by using the PRS and the NPRSbased on information on that the PRS and the NPRS can be used togetherbeing received from the base station through the transceiver, whereinthe part of the second sequence is differently determined based onwhether the cell is operated in an in-band mode or in a stand-alonemode.